1. Field of the Invention
The invention relates to a differential gear device, and more specifically, a differential gear device in which braking force is generated.
2. Description of the Related Art
Differential gear devices installed in vehicles have been proposed. For example, Japanese Patent Application Publication No. 2008-275042 (JP-A-2008-275042) describes a differential gear device that includes a differential case. The differential case includes two boss portions; holding portions that hold pinion gears; and open windows used when gears are mounted. The holding portions are formed in the differential case at two positions. In each of the holding portions, the pinion gear is provided. The holding portions are formed in a peripheral wall portion of the differential case. Each holding portion is a recessed portion that is recessed outward in a radial direction. In the differential gear device, a pinion shaft for supporting the pinion gear is not provided. Thus, the number of components is reduced.
Japanese Patent Application Publication No. 2008-14419 (JP-A-2008-14419) describes a differential device that includes a differential mechanism; and a differential control device that controls a differential action of the differential mechanism. The differential mechanism includes a differential case; pinion shafts inserted into through holes formed in the differential case; pinion gears supported by the pinion shafts; and side gears that engage with the pinion gears.
The differential control device includes an electromagnetic actuator; a dog clutch; a return spring; and a controller.
Japanese Patent Application Publication No. 2002-364730 (JP-A-2002-364730) describes a differential device that includes a bevel gear differential mechanism. The differential mechanism includes pinion shafts connected to a differential case via intermediate members; pinion gears provided on the pinion shafts; and output-side side gears that engage with the pinion gears. The differential device includes friction clutches disposed between the output-side side gears and the differential case; an actuator that presses the clutches; and a transmission member that transmits the pressing force to the friction clutches. Differential limiting force is generated using the friction clutches and the like.
Japanese Patent Application Publication No. 9-184561 (JP-A-9-184561) describes a differential device that includes a differential case; differential pinion shafts provided in the differential case; and differential pinion gears provided on the differential pinion shafts. The differential pinion shafts are slidably provided in the differential case. In the differential device, lubricating oil is supplied from the outside of the differential device, to sliding portions between the differential case and the differential pinion shafts. This prevents seizing of the differential pinion shafts.
In the differential gear device described in the publication No. 2008-275042, the number of components is reduced. However, the publication No. 2008-275042 does not describe any configuration for limiting differential action.
The differential control device provided in the differential device described in the publication No. 2008-14419 includes the electromagnetic actuator and the like. Therefore, the size of the differential device is increased.
In the differential device described in the publication No. 2002-364730, the differential limiting force is generated using the friction clutches, the actuator, and the transmission member. Accordingly, the above-described friction clutches and the like need to be provided in the differential device. Thus, the size of the device is increased.
The differential device described in the publication No. 9-184561 does not include a configuration for limiting the differential action.